1. To make filling, place pork, crab meat, lemon grass, galangal or ginger, fresh coriander, lime leaves, garlic, ground coriander, cumin, egg white and fish sauce in a food processor and process until smooth.
2. Steam or microwave spinach leaves until they are just soft. Roll 2 tablespoons of filling into a ball and place in the centre of each spinach leaf. Fold leaf around filling to enclose.
3. Half fill a clean wok with hot water and bring to the boil. Place balls in a bamboo steamer lined with nonstick baking paper. Cover steamer, place on a wire rack in wok and steam for 10-12 minutes or until cooked through.
4. To make sauce, place sugar, lemon grass, galangal or ginger, chillies, water, lime rind and juice and fish sauce in a saucepan and cook, stirring, over a medium heat for 10 minutes or until sauce reduces slightly. Remove lemon grass and galangal or ginger and discard. Serve sauce with rolls.